Those aren't maggots in your grass. They're grubs, the larvae of scarab beetles, and they're eating the roots of your lawn. Different species of grubs exist, but if your grubs look like maggots, that means they're white grubs. Because grubs live and eat underground, they usually go unnoticed. The telltale sign is disintegration of the turf, where the grubs are probably visible because you're overwatering. That's when they come to the surface.
White grubs are 1/2 to 1 1/2 inches long and have three pairs of legs near the head. You'll find them resting in a C-shape. Hatching from eggs in the soil, they pass through three life stages called larval instars. It's the third instar that wreaks the most damage on your lawn. To compound the problem, they might remain in this stage for years. The adult scarab beetle rarely disturbs the turf, but it might dine on tree leaves and make mounds in the soil, according to the University of Florida.
Diagnosis of an Infestation
When white grubs go undetected, there are other ways to diagnose the problem. Damage to your turf is most noticeable from mid-August through September, when you'll notice a gradual thinning and weakening of the lawn. Dead or wilting grass appears next, even though you're watering regularly. To make an accurate diagnosis, slice a 1-foot-square of turf with a knife or shovel and peel it back. If there are three to five grubs per square foot, implement treatment.
Preparation Before Treatment
To ensure a successful treatment with any grub insecticide, prepare the turf first by mowing the grass and raking out dead thatch so the product can penetrate the soil. After applying the chemical, water the lawn to a depth of 1/4 to 1/2 inch to leach the chemical down to the grass roots, where the grubs are feeding.
After grubs have been eating and damaging the turf, begin curative treatment by applying products made for use, available at most home and garden center. The labels will state specific uses and application procedures and amounts. The white grubs will die in the soil. Since this curative has a short residual, however, a second application may be required, advises the University of Florida.
After eliminating the grubs, you'll need to use a preventative treatment so newly laid eggs can't survive. Preventative treatments, also available at home and garden centers, come in the form of long residual insecticides.